The manufacture, assembly and use of tubular systems in drilling and constructing wells, frequently involves operations where the tubular work piece must be gripped and handled to enable the application of axial and torsional loads. Devices employing jaws, such as elevators, tongs or pipe wrenches are commonly used to engage the pipe body directly, with the risk of damage by distortion of the pipe or marking by the jaw faces. Where the tubular ends are threaded, adapters may be used to temporarily engage the threads and transfer load running the risk of damaging the threads. The present invention provides a means to internally friction grip a tubular work piece with an expandable cage, and apply assembly, handling and drilling loads through an attachment.
Historically, petroleum drilling rigs have used an architecture where drilling torque is applied through a rotary table placed in the derrick floor. The rig mast is used to support the block and tackle equipment for hoisting tubular strings comprised of individual joints of pipe connected by threaded connections, in and out of the drilled hole or well. With this architecture, it is inconvenient to use the rotary table to apply torque to make up or break out the connections. Tongs are therefore typically used to apply and react make up or break out torque, by externally gripping the pipe ends to be connected directly above and below the threaded connection. This well known procedure is used to make up and break out drill pipe, casing and tubing to trip tubular strings in or out of the well. In the case of casing and tubing, the method is typically incorporated into devices, referred to as power tongs, which provide a means to apply continuous rotation and torque through a motor and gear box assembly. However these devices still require external grips, typically using some form of jaws as described, for example, in U.S. Pat. No. 5,172,613. Whether powered or not, this method requires that one tong grip the upper end of the pipe joint suspended from the rotary table in the derrick floor, to provide a reaction for the torque applied through a second tong which is used to grip and rotate the pipe joint being made up or broken out. The upper end of the pipe joint being rotated is supported by an elevator, hanging from the travelling blocks, thus allowing rotation and providing limited freedom to translate laterally.
However recent advances in drilling rig technology have resulted in increased use of rigs having a new architecture, and known in the industry as top drive rigs. As the name suggests, these rigs are equipped with a hydraulic or electric drive head unit that moves up and down the rig mast constrained by a track, thus enabling the application of rotational force from any position. These rigs employ a drive head capable of applying torque and axial load to the top of the pipe through an output shaft known as a xe2x80x9cquill,xe2x80x9d and typically employ more automated and powered pipe-handling equipment than conventional rigs. This configuration allows the tubulars to be made up and broken out using the top drive to rotate and apply torque to the top joint, but necessitates a method of coupling the quill to the tubular capable of transmitting full make up or break out torque and at least some axial load.
For tubing and casing, this is typically accomplished using a threaded make up adapter, commonly referred to as a xe2x80x9cnubbinxe2x80x9d, threaded on the lower end to match the tubing or casing thread and on the upper end to match the thread on the quill. A device capable of stroking up and down and transmitting torque, commonly referred to as a floating cushion sub, is also often placed between the quill and the nubbin to accommodate thread make up and break out length change without top drive movement. This laterally rigid and flexurally stiff device effectively forms an extension of the quill.
Unlike the conventional make up and break out method using tongs, this method of top drive make up requires extra steps to handle, install and remove the nubbin, increasing the time and consequently, the cost of running tubulars. In addition, the risk of thread damage is increased by the extra make up and break out to the nubbin required for each joint run in or out of the well.
This method of top drive make up further exacerbates the potential for connection thread damage because the rigid lateral positioning of the top drive at the top end of the joint, where it is supported during rotation. This prevents the tendency of the thread axis to xe2x80x9cself alignxe2x80x9d as otherwise occurs when the top of the joint is suspended from the cable-supported travelling block on conventional rigs, allowing relatively free lateral movement. Although the axes of the pin and box threads are generally parallel when the connection is stabbed, tolerances for rig mast position with respect to the hole axis, pipe straightness and threading can all conspire to allow significant misalignment. Under these conditions, the potential for connection damage is aggravated by alignment constraints as imposed by relatively rigid support at the upper end of joints. Contrast this with the greater freedom of motion allowed on conventional rigs when the travelling block supports the upper end of the pipe. During rotation of the connection at the lower end, this alignment constraint tends to prevent the pin and box thread axes from self aligning which results in a tendency toward xe2x80x98cross threadingxe2x80x99 of the connection when significant tolerancing errors exist, with consequent high internal contact stress and galling susceptibility. In many instances known to the inventors, this misalignment has resulted in connection damage and improperly made-up connections.
It is therefore desirable to have a method for gripping the pipe without contacting the threads and that allows the top end of the pipe to displace laterally with relative freedom.
Methods using jaws on the exterior of the pipe to apply torque without contacting the threads are numerous. As mentioned above, jaws are typically employed with power tongs. Torque activated jaws such as described in U.S. Pat. No. 5,172,613, are the most typical architecture but the tendency of this method to mark and damage the pipe has led to more controlled active gripping systems such as described in U.S. Pat. No. 5,172,613. To further avoid xe2x80x9ccausing surface damage or structural deformationxe2x80x9d, more nearly uniformly radial loading, friction grips, such as described in U.S. Pat. No. 4,989,909 are known as a means to grip the exterior of tubulars where tolerance to damage is low. While these methods provide a generally satisfactory means for gripping the exterior of pipe, they are not amenable to use in conjunction with a top drive. Gripping the interior of the pipe avoids the need to apply torque through the coupling, or to invoke more complex means to bypass the connection, while all the time avoiding interference with other pipe handling equipment, such as elevators. Neither do these methods address intolerance to connection thread misalignment, which is peculiar to the top drive make up and break out method.
The device/method of the present invention was therefore conceived specifically as a means to friction grip the inside of the tubular and thus provide the capacity to transfer torque and carry most of the axial handling loads presently provided by nubbins. It will also shorten the handling time requirements, eliminate nubbin contact with the threads, and provide increased lateral compliance to accommodate the tendency for top end of the pipe to move off axis during make up.
To meet these objectives, the method of the present invention makes use of a device having an upper end provided with a crossover sub to attach to the quill and having a lower coupling end provided with a grip assembly, which may be inserted into the top end of a tubular work piece to be handled, and expanded to engage or grip the inside surface of the tubular joint. The grip method and contacting element preferably frictionally engage the inside wall of the tubular with a uniform distribution of radial loading virtually eliminating the risk of marking or distorting the pipe or connection. It will be understood that such attachment to the top drive quill may be direct or indirect to other intermediate components of the drill string such as a xe2x80x98thread saver subxe2x80x99 essentially forming an extension of the quill.
The upper adapter is coupled to the grip assembly by means of a tube having upper and lower universal joints which enable lateral movement during transmission of torque, as is commonly employed in applications where torque is transmitted over some length, such as in automobile drive shafts flexibly coupled through universal joints. The grip assembly is further arranged to permit the grip to be activated, or set, by application of right hand torque and deactivated or released by application of left hand torque when a first operating mode is engaged. In a second operating mode, either left or right hand torque is transferred directly through the grip without changing the grip force. The first or setting mode is engaged by application of slight axial compressive load, or by setting the quill down. The second or direct torque mode is engaged by application of slight tension or by lifting the quill up once the grip is set. These simple, fast and direct means of gripping and releasing provide substantial operational improvements over the existing methods.
The primary purpose of the present invention is to provide a method employing an internal gripping device for handling tubular work pieces in general and particularly suited to perform make up and break out of pipe joints being run in or out of a well with a top drive drilling rig, having as its gripping mechanism a sub-assembly comprised of:
1. a generally cylindrical expandable cage with upper and lower ends,
2. a structural member is provided in the form of a mandrel. Mandrel has upper and lower ends placed coaxially inside the cage where the lower ends of the mandrel and cage are attached, and where the external diameter of the cage is somewhat less than the internal diameter of the tubular work piece to be gripped, allowing the cage to be positioned within the tubular work piece,
3. a significant annular space between the inside surface of the cage and the outside surface of the mandrel,
4. a pressure member disposed in the lower interval of the annular space between the mandrel and cage as an expansion element and
5. means to activate the expansion element to cause the cage to expand and frictionally engage the inside surface of the tubular work piece with sufficient radial force to enable the mobilization of friction to transfer significant torque and axial load from the upper end of the mandrel through the cage to the tubular.
Said expandable cage of the gripping mechanism having a lower and upper end:
is preferably comprised of a plurality of flexible strips aligned largely axially along the body of the cage and attached to cylindrical sleeves at each end of the cage,
where the edges of adjacent strips are preferably profiled to provide interleaving tabs or fingers,
which fingers permit cage expansion or radial displacement of the strips but tend to prevent cage twist or shear displacement between strips under torsion loading.
Said means to provide cage expansion is preferably provided by:
a largely incompressible elastomeric material disposed in the lower interval of the annular space between the mandrel and cage,
means to confine the ends of the elastomeric material and if necessary further means to confine the outer sides of the elastomeric material across gaps that may exist between adjacent edges of the cage strips to prevent excess extrusion of the elastomeric material when compressed, and
means to axially compress the annular elastomeric material with sufficient force to cause the cage to expand and frictionally engage the inner surface of the tubular enabling transfer of torque and axial load from the upper end of the mandrel through the cage to the tubular.
An additional purpose of the present invention is to provide a tubular gripping and handling device having said gripping sub-assembly joined to an external load and torque application device, such as the quill of a top drive rig, through a load transfer member or drive shaft, flexibly coupled at each end where such flexible couplers function as universal joints enabling transfer of torque with little or no moment or lateral resistance.
This purpose is preferably realized by:
providing a crossover sub configured to thread to the quill on its upper end and connect to a tubular or hollow drive shaft at its lower end,
by means of pins engaging slots in the upper end of the drive shaft thus providing the function of a universal joint, where
a similar slotted and pinned connection is provided to join the lower end of the drive shaft to the upper end of the gripping mechanism sub-assembly.
A further purpose of the present invention is to provide a means to flow fluid and apply pressure through the top drive adapter and into the tubular work piece being gripped. This purpose is realized by providing a flow path through the crossover sub, drive shaft and tool mandrel and is preferably augmented by provision of an internal cup seal, such as a packer or swab cup, attached to the lower end of the mandrel to prevent leakage into the annular space between the mandrel and inside surface of the tubular work piece.
In applications, where the lifting capacity of the frictional grip is insufficient to reliably support the hoisting loads required to run assembled tubular strings into or out of a well, the make up and break out functions provided by the tubular handling and gripping assembly, must be supplemented by the addition of hoisting equipment. In a manner well known to the industry, such hoisting equipment may be provided as elevators. However, to support applications where suitable elevators may not be available or convenient to use, it is a further purpose of the present invention to provide additional means to support hoisting loads, integral with the frictional grip device.
This purpose is realized by providing an external hoisting sub-assembly, which sub-assembly is comprised of:
a largely cylindrical hoisting sleeve coaxially placed outside the internal gripping subassembly having an upper end attached to the upper end of the internal gripping subassembly, a lower end extending downward to overlap an interval of the tubular work piece, typically to the lower end of the collar typically attached to the upper end of casing or tubing joints, and lower end configured with internal grooves,
a plurality of jaw segments, preferably provided as a collet where the upper end of the collet fingers are attached, and the lower end of the collet fingers carry the jaw segments configured to mate on their interior with the outside surface of the tubular work piece and on their exterior with ribs engaging the internal grooves of the hoisting sleeve where the spring action of the collet is preferably arranged so the jaws tends to contact the work piece,
where the mating ribs and grooves of the jaw and hoisting sleeve surfaces respectively tend to force the jaws inward under application of hoisting load, in the manner of slips, well known to the industry as a method of providing load transfer between hoisting equipment and tubular goods, and
means to retract the jaws to facilitate disengaging from the tubular work piece, which means is preferably linked to the operation of the internal friction grip so that the jaws may only be retracted when the tool is not set or activated.